This invention relates generally to the testing of electrical integrated circuits, and more particularly the invention relates to sockets for receiving packaged integrated circuits for test purposes.
The packaged integrated circuit typically includes a polymer or ceramic housing for a semiconductor chip with electrical leads extending from the package which are electrically connected to the semiconductor chip. In a dual in-line package (DIP), the electrical leads are arranged in two parallel rows with the leads depending from the bottom of the housing.
Packaged integrated circuits must undergo a number of different tests, each test requiring the insertion of the integrated circuit package and leads into a test socket. To prevent bending or damage to the leads, zero insertion force (ZIF) sockets have been devised to limit the force exerted on the leads when the package is inserted into a test socket. The most widely known and used ZIF sockets are from 3M Corporation and Aries Corporation. In these sockets the leads of a DIP (dual in-line package) are pinched between two pieces of metal which are, in turn, soldered to a printed circuit board. The metal pieces are held in place by the body of the ZIF socket which is typically made of plastic. The metal pieces are electrically conducting to provide a good electrical path from the DIP lead to the printed circuit board in which the ZIF socket is attached. In all cases, the bodies of these sockets are made of some organic material (plastics or polymers) which can only withstand temperatures as high as 250xc2x0 C. for extended periods of time. The metal used to pinch the leads of the IC DIP packages are beryllium copper alloy or beryllium nickel alloy for a high temperature operation not to exceed 250xc2x0 C. While these sockets perform well within their stated specifications, they cannot be used at temperatures in excess of 250xc2x0 C. because the materials will decompose and fail.
FIG. 1 is a top view of the ""640 patent socket in an empty position. The socket 8 includes a bottom plate 10 and a top plate 12 (shown by outline) with the lower plate including two arrays of parallel wires 14, 16 which are respectively anchored to bottom plate 10 in holes at anchor points 20, 21 and anchor points 22, 23. Top plate 12 includes two rows of holes 18, 19 for receiving pins of a dual inline pin (DIP) package. A yieldable metal spring 24 maintains top plate 12 positioned on bottom plate 10 with wires 14, 16 centrally disposed over holes 18, 19. The bottom plate has elongated slots (not shown) through which package pins extend. In this socket design, the bottom plate is fixed, while the top plate is made laterally translatable with respect to the bottom plate by means of a cam drive.
FIG. 2 shows the socket in an actuated position with the top plate moved laterally to the right against spring 24 with holes 18, 19 moved from wires 14, 16. In this position the Unit Under Test (UUT) pins can be placed in the holes or withdrawn from the holes without the wires obstructing the pins. Once pins are inserted in the holes, and the actuating force is removed, spring 24 will then push the top plate to the left whereby the pins engage wires 14, 16.
FIGS. 3A, 3B show UUT 28 positioned in the socket with pins 30, 32 engaging wires 14, 16. In FIG. 3B UUT 28 is removed to expose the underlying interaction between the pins 30, 32 and wires 14, 16.
The present invention is directed to such a ZIF socket, but in which the top and bottom plates are fixed and a wire actuator is employed for inserting and removing a UUT.
In accordance with the invention, a ZIF socket has top and bottom plates which are attached in a unitary structure, and an external wire actuator is employed for inserting and removing a UUT. The top plate has first and second rows of holes for receiving UUT pins with the holes aligned with the contact wires. Larger third and fourth rows of holes are provided for receiving pins of the actuator which engage and laterally flex the wires for inserting and removing a UUT.
In one embodiment, the actuator comprises a rectangular-shaped body with an open central portion through which a UUT package can pass. The body has two rows of pins depending therefrom for insertion into the third and fourth rows of holes in the socket and engaging the wire contacts. Each pin of the actuator preferably has a tapered point for facilitating the engagement with a wire contact.
In another embodiment, the actuator comprises a frame with depending pins which are received in the third and fourth rows of holes. The frame is laterally translatable by means of a screw or lever, for example, whereby the depending pins can engage and flex the wires for inserting and removing a UUT.
By using a wire actuator in accordance with the invention, the ZIF socket has a simplified design and can be more economically manufactured.
The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawings.